Is there any particular reason other than price that you're not using Jace 2.0 instead of Beleren? Also, I'd consider scrapping the Sphinxes for more Baneslayers. Also, maybe Wall of Denial as opposed to Omens. It costs more, but you can't argue with 0/8 Flying Shroud. The draw a card is nice for Omens, but still.
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I've found that in decks with Bloodghasts, Eldrazi Monument works pretty spectacularly. Especially if you can keep triggering the landfall, maybe via Marsh Flats or Terramorphic Expanse. Also, maybe Butcher of Malakir instead of Hellcarver Demon to go along with that (and Bone Splinters). It's slightly more expensive, and obviously has a different style associated with it, but if you're losing a creature every turn with Eldrazi monument, it's nice that they have to too. And doubling the effectiveness of Bone Splinters can't be bad. One last thing, Crypt of Agadeem might help you just a bit in trying to accelerate your mana. Sorry for running on.
With the disentombs I don't think you need 24 creatures, so I'd suggest maybe taking out the Guul Draz and adding in Blades of the Bloodchief. It's not a great creature early on, though it be cheap enough, but with Blades, you can make the Nighthawks just flat out sick (especially if you double up).
Gotta say, Tendrils IS awesome, but it's useful to have something that only costs 2 that can still kill a creature and gain you some life (and ideally deal some damage again). If you look at your mana curve currently, you've got a fairly fast deck, why make it worse? I'd say keep in the feasts and leave tendrils for a late game-ender. Also, I think maybe you have too many Drana, Kalastria Bloodchief. Maybe swap out two for the Aristocrats like 4GGRO! suggested?
Sorry, the minimum cast for Tendrils in that situation is 5, not 4 because of the Bond.
I would have to suggest Marsh Flats instead of Evolving Wilds. Yes, you lose a life to do it, but with the nighthawks, tendrils, vapors and such, who cares? At least with Marsh Flats you can still use that land that turn. I would also recommend maybe adding in Blade of the Bloodchief for something, because it really is just too sick not to use. Maybe two of them in the place of two Bloodghasts? If you think about it, as long as they've been out, it's not like the bloodghasts are going to run out at any point, and you've got enough other stuff that you don't need four of them. Might be worth it, just to think about, sideboarding Sanguine Bond because of all of the life gain stuff you have there. Minimum casting state for Tendrils is 4 damage to a creature, 4 life to you, and 4 damage to your opponent, and it just gets better from there. One last thing, almost certainly should have Feast of Blood instead of Urge to Feed. Coupled with Blades and Sanguine Bond, it's just great, and how likely is it that you won't have the two vamps out for its cost?